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Flashcards in Chemosensation Deck (21)
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1
Q

Aguesia

Dysguesia

A

aguesia: loss of sense of taste
Dysguesia: altered perception of taste (often persistent bad or salty taste)

2
Q

anosmia

A

loss of sense of smell

3
Q

hyposmia

A

diminished sense of smell

4
Q

dysosmia

A

altered or distored sense of smell

5
Q

parosmia

A

altered preception of smell in presence of an odor usually unpleasant

6
Q

phantosmia

A

perception of smell without an odor present

7
Q

Basic tastes and taste receptors

A

sour: ion channel (pH)
salty: ion
sweet: GPCR (carbs)
bitter: GPCR
umami (savory): GPCR (indicates presence of glutamate from animal origin–proteins)

8
Q

Chemosensory systems

A

taste
smell
chemesthesis (trigeminal)

9
Q

“Taste” sensation

A

stimulation of 3 sensory systems:

  1. olfaction
  2. gustation
  3. chemesthesis (detection of irritant chemicals by trigeminal nerve endings–capsaicin, CO2)

-use taste buds in tongue/palate

10
Q

Olfactory receptor neuron location

A

-neuroepithleium lining the roof of the nasal cavity

11
Q

Smell:
receptor cell
cranial nerve
primary sensory nucleus

A

receptor cell: ciliated, bipolar neuron
cranial nerve: I
primary sensory nucleus: olfactory bulb

12
Q

Taste:
receptor cell
cranial nerve
primary sensory nucleus

A

receptor cell: modified epithelial cell (synapses onto nerve fiber from cranial ganglion cell)
cranial nerve: VII, IX, X
primary sensory nucleus: nucleus of the solitary tract

13
Q

Chesthesis
receptor cell
cranial nerve
primary sensory nucleus

A

receptor cell: free nerve ending of cranial ganglion cell
cranial nerve: V
primary sensory nucleus: spinal trigeminal nucleus

14
Q

Taste receptor cells

A

-Found in taste buds (tongue, soft palate, oropharynx, epiglottis)
-Lingual taste buds on taste papillae.
fungiform papillae (anterior tongue)
foliate papillae (sides)
circumvallate papillae (posterior part of tongue)

Filiform papillae are non-taste papillae and serve as tactile organs

Chorda tympani of facial n innervates fungiform pap in anterior 2/3 of tongue, glossopharyngeal inn circumvallate

taste buds in soft palate: sup petrosal br of facial n
Oropharynx and epiglottis buds: vagus

each taste bud has 50-100 cells, only some express receptor proteins; limited lifespan/replaced.; tast cells make functional contact with VII, IX, X fibers

15
Q

Excitation of taste cells

A
  • Tastants reach elongate receptor cells through taste pore
  • depol leads to transmitter release from basal portion of cell.
  • ATP acts on P2X receptors
  • individual taste receptor cells are sensitive mostly to one class of taste stimuli.
  • CNS extracts info from POPULATION of cells.
16
Q

Where are taste receptors expressed?

A

in many cells of the body:

airways (nasal cavity, trachea, bronchi) use bitter recep to detect and respond to bacterial signaling molecules.

17
Q

Central taste pathways

A
  • afferents from tongue run in facial (VII), glossophar (IX), and vagus (X) nerves
  • enter CNS, synapse on second order neurons in the rostral area of ipsilateral nucleus of solitary tract (NST)
  • second order cells of NST send axons bilaterally to medial part of ventrobasal thalamus
  • thalamic neurons–>insular cortex
  • secondary gustatory cortex (orbitofrontal face–integration of taste and flavor) receives projections from primary gustatory area located on anterior insula and from olfactory areas of insula
  • NST also relays taste info to hypothalamus and amygdala for reg of food intake and visceral rxns to foods.
  • Also: NST projects to brainstem for gagging (nuc ambiguus), swallowing (nuc ambig, hypoglossal nuc), and salivation (sup and inf, salivatory nuc)
18
Q

Olfactory neuroepithelium

A

covered with mucus

  • olfac neurons extend cilia into mucus (cilia=large surface area)
  • odorants dissolve in mucus and interact with olfactory receptor proteins
  • cilia conver chem to elec info.
  • Olfactory neurons=bipolar
  • olfactory neurons are exposed to external environ
  • olfactory neurons are the only neurons that are continuously undergoing neurogenesis and replacement (vulnerable to mitotic inhibitors like in cancer tx)
19
Q

Olfactory transduction

A
  • olfactory receptor protein on olfac cilia.
  • GPCR
  • subfamilies of recep may bind distinct structural classes of odor stimuli
  • Odorant binds to receptor protein, associated G-prot activates adenylyl cyclase generating cAMP
  • cAMP opens gated ion channel (Ca, Na enter)
  • Ca opens Ca gated Cl channel (outflow of Cl, depolarizing cell)–> AP.

-Kidney and lung also have functionng olfac receptors

20
Q

Olfactory bulb

A
  • signals from olfactory neurons are processed in olfactory bulb.
  • Axons of olfactory neurons penetrate ethmoid bone (cribriform plate) and converge on glomeruli on outer layer of olfac bulb (thousands of axons in each glomeruli from a single olfac neruon make excitatory synapses)
  • olfactory receptor neurons expressing the same olfactory receptor protein project axons to the same glomerulus
  • *Primary principle of encoding odor quality is through a odor-related map of glomeruli in the olfactory bulb (whereas in olfactory epithelium, receptor cells w/ common receptor are scattered)
  • But each odorant can stimulate mult. receptors–>mult glomeruli
  • Odor identific: recogonition of PATTERN of activity across all glomeruli
21
Q

Central olfactory pathways

A

Output of olfactory bulb do NOT travel thru thalamus before reaching cortex.

-Bulb–>tract–>olfactory cortex and amygdala.

Cortex: lateral olfactory gyrus and part of uncus
Olfactory cortex: piriform cortex, accessory olfactory nucleus, and olfactory tubercle.

Olfactory tract projects to:

  • Piriform cortex projects to the orbitofrontal cortex (assoc area for olfactory and taste info–conscious perception), directly and indir via MD nucleus of thalamus
  • Amygdala and olfactory tubercle are interconnected with the hypothalamus (visceral rxns and homeostasis)
  • entorhinal cortex feeds into hippocampus (player in storage and retrieval of memory)